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The taxonomic uncertainty surrounding cryptic species complexes has traditionally been resolved using lengthy experimental approaches, while, since the advent of PCR based techniques the number of cryptic species described in a variety of taxa is increasing steadily. Here we formally describe a new rotifer species of the Brachionus plicatilis complex: Brachionus manjavacas n.sp., disentangling what was known as a morphological stasis. Detailed morphological analyses demonstrated significant differences in body shape and size between B. manjavacas and B. plicatilis s.s., analysed by geometric morphometrics; unfortunately these statistical differences are not taxonomically reliable because of wide overlaps. Size and asymmetry of masticatory apparatus, named trophi, observed by SEM, gave similar results, with taxonomic ambiguity. Only the shape of small pieces of the trophi, named satellites, were consistently different between the species. On a strictly classical taxonomical basis it is absolutely useful to name new species on morphological bases, as we did, and to assess their status as distinct entities. Nevertheless, the two species are broadly similar; therefore, we do not suggest using the small differences in shape of satellites of trophi to identify the species for further ecological studies, but to continue discriminating them on genetic marker bases. [ABSTRACT FROM AUTHOR]

Authors have attributed the statement "All science is either physics or stamp collecting" to the Physicist, Ernest Rutherford. Putting this sarcastic quip aside, we know that scientific disciplines come of age when they can generate testable, repeatable, and falsifiable hypotheses; yet disciplines begin, and continue, by simply collecting observational information. It is clear, even with a casual assessment of all 16 International Rotifer Symposia, as well as the extensive literature published since our first congress, that rotifer research has moved beyond describing species, making lists of their occurrences, and describing changes in their population dynamics. In spite of the excellent progress that has been made in rotiferology we believe more remains to be done. In this review we nominate 10 fields in rotifer research that we believe will advance understanding of rotiferan biology; these include the following topics: (1) neurobiological connectomes, (2) genomic architecture and control systems, (3) physiology, (4) life history, including sexuality, development, and aging, (5) ecological responses to stresses, (6) biogeography and distribution of cryptic species, (7) analysis of rotiferan morphospace, (8) rotifer evolution within Gnathifera including Acanthocephala, (9) educational opportunities for beginning students, and (10) fostering international collaboration. [ABSTRACT FROM AUTHOR]

Interactions between rotifers and their insect predators have not received adequate attention, possibly due to the assumption that rotifers are too small for insects to eat. In laboratory experiments, we offered the rotifers Hexarthra mira, Plationus patulus and small and large Synchaeta pectinata to four common insect predators: the notonectids Notonecta lunata and Buenoa macrotibialis, the smaller hemipteranNeoplea striola and small (1.5 mm) aeschnid dragonfly larvae. Excepting Plationus offered to dragonflies, all rotifer preys were consumedto some degree. No size selectivity was apparent for predators that ate few rotifers, but small instar Buenoa ate significantly more large (420 Mum) than small (300 Mum) Synchaeta. Predator size appeared tobe less important than predatory style and prey morphology in determining ingestion rates. Neoplea and dragonflies ate more Hexarthra than Plationus, while the pattern was reversed for Buenoa, possibly because Buenoa is able to manipulate the hard lorica of Plationus better.Insect predators are capable of direct suppression of rotifer populations, an interaction which may be particularly important in littoralzones and fishless ponds where macroinvertebrates are numerous. [ABSTRACT FROM AUTHOR]

Information on the distribution of three genera of rotifers, Anuraeopsis, Brachionus, and Notholca of the family Brachionidae in the Ural region is summarized based on the author's research and the analysis of published sources. Data on their localities, biology, and quantitative development in water bodies of the Ural region are presented. [ABSTRACT FROM AUTHOR]

Molecular techniques are gaining importance in biodiversity conservation in India. They are especially beneficial in the case of rare species with cryptic habits that make them difficult study subjects when using conventional field techniques. Molecular tools can be used to decipher distributions and population connectedness in fragmented habitats and identify populations of immediate conservation concern. We discuss these with case studies on some cat species in India. [ABSTRACT FROM AUTHOR]

Members of the family Brachionidae are free-living organisms that range in size from 170 to 250 microns. They comprise part of the zooplankton in freshwater and marine systems worldwide. Morphologically, members of the family are characterized by a single piece loricated body without furrows, grooves, sulci or dorsal head shields, and a malleate trophi. Differences in these structures have been traditionally used to recognize 217 species that are classified into seven genera. However, the validity of the species, Plationus patulus, P. patulus macracanthus P. polyacanthus, and P. felicitas have been confused because they were alternatively assigned in Brachionus or Platyias, when considering only morphological and ecological characters. Based on scanning electron microscope (SEM) images of the trophi, these taxa were assigned in a new genus, Plationus. In this study, we examined the systematic position of P. patulus and P. patulus macracanthus using DNA sequences of two genes: the cytochrome oxidase subunit 1 ( cox1) and domains D2 and D3 of the large subunit of the nuclear ribosomal RNA (LSU). In addition, the cox1 and LSU sequences representing five genera of Brachionidae ( Anuraeopsis, Brachionus, Keratella, Plationus, and Platyias) plus four species of three families from the order Ploima were used as the outgroup. The maximum likelihood (ML) analyses were conducted for each individual gene as well as for the combined ( cox1 + LSU) data set. The ML tree from the combined data set yielded the family Brachionidae as a monophyletic group with weak bootstrap support (<50%). Five main clades in this tree had high (>85%) bootstrap support. The first clade was composed of three populations of P. patulus + P. patulus macracanthus. The second clade was composed of a single species of Platyias. The third clade was composed of six species of Brachionus. The fourth clade included a single species of the genus Anuraeopsis, and the fifth clade was composed of three species of the genus Keratella. The genetic divergence between Plationus and Platyias ranged from 18.4 to 19.2% for cox1, and from 4.5 to 4.9% for LSU, and between Brachionus and Plationus, it ranged from 16.9 to 23.1% ( cox1), and from 7.3 to 9.1% (LSU). Morphological evidence, the amount of genetic divergence, the systematic position of Plationus within the family Brachionidae, and the position of Plationus as a sister group of Brachionus and Platyias support the validity of Plationus patulus and P. patulus macracanthus into the genus Plationus. [ABSTRACT FROM AUTHOR]

The fish fauna and its relationships with physiography and climate were studied in northwestern Argentina from 21°30′ S to 26°30′ S and 63°30′ W to 65°50′ W, an area about 10,276 km2. Along a southeast–northwest gradient, the Chaco forest at low altitudes gives way to the Yungas cloud forest in highlands, and then, to an increasing desertic landscape, with xerophytic vegetation and scarce rainfall along the Grande River. Finally, extreme desert conditions prevail in the most northern part at the Puna plateau. Water chemistry was sampled from sites from 400 to over 3800 m a.s.l. In all 3278 fish specimens of 52 species were collected. Previous lists included 84 species. Only 19 were shared, meaning that 40 species are new for the area and/or particular localities, including 7 reports from Aguas Calientes. These results increase by one third the number of species in northwestern Argentina. The fish fauna was represented by eurytopic species of Paranensean genera as Astyanax, Bryconamericus and other characoids, mixed with locally distributed siluriforms. Under extreme climatic conditions, species of Trichomycterus predominate. Species assemblages show a combination of a large number of species typical of, sometimes endemic to or rather abundant in, the area, combined with a few species of Paranensean character. Fish assemblages were clearly defined by faunistic composition and distribution related with physiography and climate traits. A significant negative correlation is observed between both species number and abundance, and increasing altitude, and positive relationships exist with mean annual temperature and other climate traits. Diversity values (Shannon index) agree with the described pattern of increasing impoverishment of the fish fauna of northwestern Argentina, along gradients of increasing altitude and dryness and decreasing temperature. [ABSTRACT FROM AUTHOR]

Fertilized resting eggs of Australian Brachionus quadridentatus hatched 2-3 days after hydration into females with or, more frequently, without posterior lateral spines. These females then produced clones with short-spined or long-spined phenotypes. Asplanchna girodi inducedfemales from two short-spined clones and one long-spined clone to produce daughters with significantly longer posterior lateral spines. In all clones, there were significant differences in spine developmentamong offspring of mothers within Asplanchna and control treatments.The range of phenotypes reported in one short-spined clone is observed in the billabong and includes much of the variation described for the species, with mehleni (long-spined) phenotypes occurring with Asplanchna. In B. quadridentatus, the ecological significance of long-spined, basic phenotypes, and of the spine-development response to Asplanchna, is unclear. In laboratory cultures, females of all clones were attached to the substratum or water surface, and were safe from Asplanchna; in nature, females are epiphytic and probably rarely susceptible to Asplanchna. Most (96%) resting eggs produced in cultures and kept under culture conditions hatched after a 7-day latent period. This raises questions regarding natural conditions which might prevent hatching and allow accumulation of resting eggs in a sediment egg bank. Hatching of resting eggs in nature may be enhanced in sediments which dry and then become flooded after rains. [ABSTRACT FROM AUTHOR]